Zirconium Phosphate (ZrP) is used during sorbent dialysis to absorb ammonium ions generated by the reaction of urease breaking down urea in dialyzed blood. The ZrP layer is oftentimes provided as a specific layer in a sorbent cartridge used during dialysis. However, urease is generally not expended before ZrP is exhausted during dialysis. As such, if a patient has a large amount of urea in the blood, which generates a large amount of ammonia from urease, the ZrP layer may not be able to adsorb all the ammonia generated by the urea. In that case, a sorbent cartridge's capacity to adsorb ammonia has been reached resulting in so-called “ammonia breakthrough.” Ammonia may then enter the dialysate fluid, which is returned to the patient. Because ammonia is toxic, dialysis must be halted and the cartridge replaced.
In order to avoid ammonia breakthrough during therapy, oftentimes more zirconium phosphate is provided than is normally necessary, thereby ensuring that almost all patients can receive therapy without ammonia breakthrough. This provides enough zirconium phosphate for the majority of patients, but increases costs and waste by using more of the zirconium phosphate than is necessary.
Known dialysate fluid circulation systems and apparatuses have systems in place to halt dialysis in the event of ammonia breakthrough. In other systems, additional zirconium phosphate may be added in order to continue dialysis. An alternative to stopping dialysis involves bypassing a module containing urease, and thereby stopping the process of creating ammonia. However, although other toxins can continue to be removed from the patient, urea is no longer removed from the dialysate. In order to minimize the frequency of ammonia breakthrough, some sorbent cartridges use more zirconium phosphate than is necessary for most patients. This allows dialysis to continue as normal for larger or more uremic patients. However, providing more zirconium phosphate than is necessary for most patients results in increased costs and waste along with larger and more cumbersome cartridges. Customizing sorbent cartridges for larger or more uremic patients likewise increases costs. Alternatively, expensive sorbent materials have been used to remove ammonia from spent dialysate. However, the systems do not provide for recharging some or all of the components of a sorbent cartridge that would allow reuse of specific components to enable lower long-term costs for operating such systems.
As such, there is a need for removing urea without halting dialysis or risking harm to a patient in the event of ammonia breakthrough. There is also a need for improving the effectiveness and efficiency of a sorbent cartridge by reducing the amount of expensive, rate-limiting sorbent materials used during dialysis. There is a need for avoiding ammonia breakthrough during therapy without providing more zirconium phosphate than is required while ensuring that almost all patients can receive therapy without ammonia breakthrough. There is a need for avoiding increased costs and waste by avoiding using more of the zirconium phosphate than is necessary for safe dialysis. There is a further need for a sorbent cartridge and related systems and methods having a reserve module containing a sorbent material capable of removing ammonia from dialysate so that dialysis can continue in the event of ammonia breakthrough. There is a need for a sorbent cartridge providing for the use of a reserve sorbent module to allow normal operation with a smaller amount of sorbent material, while at the same time ensuring that ammonia breakthrough does not occur.